Plural of electro; coins or medals made from an alloy of gold and silver, or electronic devices/records.
From electro (originally from Greek elektron 'amber', later 'alloy of gold and silver'). The plural form entered English through both numismatics and modern electronic terminology.
The ancient word 'electros' originally meant that golden-silver blend found in Lydia (modern Turkey), and archaeologists believe amber's electrical properties gave it its name—so the word for electricity comes from the ancient word for a specific metal alloy!
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